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An Introduction to Direct Methods.

The Most Important Phase Relationships and their Application in Solving the Phase Problem.

H. Schenk

Laboratory for Crystallography, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WN, Amsterdam

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• Introduction
• Notation
• Strong and Weak Structure Factor Magnitudes F_H
• Normalized Structure Factors E_H
• The |E|'s of H and 2H: The $\sum_1$ Relationship
• The $\sum_1$-Relation from a Harker-Kasper Inequality
• Large |E_H|, |E_K| and |E_-H-K|: The Triplet Relationship
• The Triplet Relation from Sayre's Equation
• The Positive Quartet Relation
• The Negative Quartet Relation
• How Numerous are the Reliable Triplets and Quartets?
• Direct Methods in Action
• Additional Literature
• References

Teaching Aims

To help students, with some basic knowledge of crystallography, to understand teh principle of direct methods.

Level

This course is suitable for the first years of undergraduate study in any direction of science.

Background

Students should have understanding of Fourier analysis of the electron density, and some knowledge of the structure factor equation.

Practical Resources

No particular resources are required.

Time Required for Teaching

The course may occupy 2-5 hours of teaching.

Copyright © 1984, 1998 International Union of Crystallography